The MGA-68563 LNA is rated at +21 dBm absolute max according to its datasheet, and the Pereguine PE42641 switches +33 dBm (minimum, high VSWR).I guess the main limit is either the back to back BAV99 diodes D1 and D4 on the input or the MIRICS IC.

I'd say you should be fairly safe with +10 dBm, (and the diodes would begin to limit at about +12 dBm) but there's not a spec which states that anywhere.